Electrical contact breaker mechanisms with improved contact gap adjustment means

ABSTRACT

A contact breaker assembly for use with a distributor of a spark ignited internal combustion engine including a first electrical contact point associated with a cam follower and adapted for reciprocatory movement in consonance with the cam follower. A second electrical contact point associated with a bearer member and with hand-operable adjustment means adapted to open or close the gap between the first and second contact points. The handoperable adjustment means comprises a knurled wheel associated with resiliently biased restraining means and with a screw threaded rod adapted to progress the second electrical contact point towards or away from the first electrical contact point.

United States Patent Inventors Roland J. Yeo

40 Broadlands Road, Avondale, Salisbury; Jean E. Colley, l8, Coghlan Road,

' Greendale, Salisbury, Rhodesia Appl. No. 788,564 Filed Jan. 2, I969 Patented May 25, 1971 Priority Jan. 15, 1968 Rhodesia 408/67 ELECTRICAL CONTACT BREAKER MECHANISMS WITH IMPROVED CONTACT GAP ADJ USTMENT MEANS Primary Examiner-J. R. Scott Attorney-Wenderoth, Lind and Ponack ABSTRACT: A contact breaker assembly for use with a distributor of a spark ignited internal combustion engine including a first electrical contact point associated with a cam follower and adapted for reciprocatory movement in consonance with the cam follower. A second electrical contact point associated with a bearer member and with hand-operable adjustment means adapted to open or close the gap between the first and second contact points. The hand-operable adjustment means comprises a knurled wheel associated with resiliently biased restraining means and with a screw threaded rod adapted to progress the second electrical contact point towards or away from the first electrical contact point.

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I noenlor wuwwww Attorney ELECTRICAL CONTACT BREAKER MECHANISMS WITH HMPROVED CONTACT GAP ADJUSTMENT MEANS This invention relates to electrical contact breaker mechanisms and is particularly concerned to provide a modified form of contact breaker for use in the ignition circuits of spark ignited internal combustion engines.

The most commonly used form of contact breaker for ignition control of internal combustion engines comprises a distributor wherein a cam member rotates upon a spindle driven by the valve actuating cam shaft gear of the engine.

Within the distributor housing there is located a bearer arm which has an electrically insulated cam follower, biasing means to bring the cam follower into contact with the cam; a bearing formation towards one end of the member adapted to mate with a pivot post fast with the distributor and towards the other end of the member a metallic electrical contact point. Fast with the base of the distributor is a further electrical contact point which is adapted to mate with the first contact point to complete the breaker assembly. The second electrical contact point, frequently called the fixed contact, is adapted for limited movement in relation to the base plate of the distributor so as to allow a gap to be established between the two electrical contact points when one of the protuberances on the cam thrusts the cam follower and consequently the associated electrical point to one of the extreme positions of travel of the contact bearing member.

In. operation the crankshaft of the engine rotates and thereby rotates the cam in the distributor housing by appropriate gearing. The first electrical contact bearer member which is inherently biased towards the rotating cam will move backwards and forwards as the follower passes over the four, six, eight or more protuberances on the cam face, the number of such protuberances depending on the number of cylinders in the particular engine. Each such movement serves to bring the movable electrical contact point from a first position where it contacts the fixed electrical contact point so establishing a circuit, to a second position where it is electrically isolated from the first contact point so serving to break the electrical circuit. This action is repeated 21' predeterminal number of times during each revolution of the distributor cam. Further circuitry is provided whereby the interrupted primary electrical circuit passing through the contact points will generate a corresponding high tension electrical current in a coil, this current then being conveyed to the spark plugs situated in the combustion chambers of the cylinders.

This well-known arrangement suffers certain'defects particularly in high performance engines. One of the first defects to be observed is spring bounce or flutter which begins to be noticeable in the mechanism at about 3,000 revolutions per minute. This spring bounce or flutter, if not damped out adequately, will eventually lead to a completebreakdown of the ignition circuit at high revolutions when the bias of the leaf spring mechanisms will fail to return the contact to the closed position after it has been thrust away by a cam protuberance and before the next protuberance strikes the cam follower. More or less erratic firing develops during increase in revolutions with consequent loss of efficiency in the engine.

A further-disadvantage resides in the fact that each type of internal combustion engine tends to have designed for it a particular distributor with, for example, a greater or lesser electrical contact surface or a more or less powerful spring mechanism so as to cope with the widely varying requirements of low and high performance single and multicylinder engines. As a result of these requirements a largerange of contact points must be stocked for varying types of engines.

A further disadvantage arises from the system of placing the electrical contact points within a housing which housing serves the further purpose of distributing the high tension sparks to leads connected to spark plugs in the-cylinders. Because of this arrangement it is quite impossible to set the gap between fixed and movable contact points while the engine is running. The manufacturer therefore determines, by a LII compromise solution, the gap setting which will give the theoretical best performance" over the entire range of engine speeds expected or allowed under load conditions. This can only be a compromise and, particularly in very high performance engines, may lead to power loss at either end of the graph of revolutions versus power.

Minor disadvantages arise from the fact that the commonly used form of distributor is difficult to insulate against penetration of water or water vapor. As a consequence of water penetration the electrical circuit tends to break down with resultant failure of the ignition system. The failure may be partial or complete and will result in erratic firing or complete refusal of the engine to function.

It is with these problems that the present invention is particularly concerned and it is an objective of the invention to provide an improved form of contact breaker point which will -at least minimize the disadvantages inherent in the known systems.

According to the invention a contact breaker assembly for use with a distributor of a spark ignited internal combustion engine includes a first electrical contact point associated with a cam follower and adapted for reciprocatory movement in consonance with the cam follower; a second electrical contact point associated with a bearer member and with hand-operable adjustment means adapted to open or close the gap between the first and second contact points.

Also according to the invention; the hand-operable adjustment means comprises a knurled wheel associated with resiliently biased restraining means and with a screw threadedrod adapted to progress the second electrical contact point towards or away from the first electrical contact point.

Also according to the invention a contact breaker assembly includes a hand-operable adjustment means which comprises a pair of wheels carried on a screw threaded red one wheel acting as a locking device in association with a threaded bearer member through which the threaded rcid passesthe other wheel being fast with the screw threaded rod which is adapted to progress the second electrical contact point towards or away front the first electrical contact point.

ln one form of the invention the hand-operable adjustment means is contained within the body of the distributor andin an alternate version of the invention the hand-operable adjustment means is placed externally of the distributor body.

Still further according to the invention a contact'breaker assembly for use with-a distributor of a spark ignited internal combustion engine includes a first electrical contact point associated with a cam follower and adapted for a reciprocatory movement in consonance with the cam follower; a second electrical contact point associated with a bearer member and with hand-operable adjustment means adapted to open or close the gap between the first and second contact points and further adapted so that the first and second electrical contact points are placed externally to the distributor body in a separate housing and means is provided which is adapted to adjust the biasing of the first electrical contact point and through this the cam follower against the cam so as to minimize bounce at high revolutions.

In order to illustrate the nature of the'invention embodiments and exampleswill be describedin detail below'with reference to the accompanying drawings in which:

FIG. 1, illustrates a perspective view of a distributor of the conventional type modified by the provision of externally placed electrical contact points;

FIG. 2, illustrates a perspective view of a first preferred form of the invention;

FIG. 3, illustrates a perspective view of a second-preferred Referring to FIG. 1, numeral indicates the housing of a standard distributor for a spark ignited internal combustion engine. Removably affixed to the casing 10 by means of a clamp member 11 and wing-nut 12 there is a housing 13 adapted to support a pair of members 14 and 15 having affixed thereto electrical contact points 16 and 17. Fast with member 14 there is an arm'18 provided with a ball or roller bearing 19 adapted to ride upon cam 20. Member 14 is further provided with adjustable biasing means 21, comprising knurled wheel 21a coiled spring 21b and threaded rod 216 which allows increased pressure tobe exerted on arm 18 so as to minimize bounce at high cam revolutions.

Member 15'is also provided with adjustment means 22, comprising knurled wheel 22a, threaded rod, 221; and coiled spring.22c adapted to move member 15 and its attached electrical contact point 16 towards or away from electrical contact point 17 as desired.

A hinged cover 23 is provided to exclude dirt or moisture from housing 13 and a hinged lower cover 24 is adapted to support an electricalcondenser 2S. Wing-nut 26 acts to clamp both cover 23 and cover 24 to form an enclosure. A window 26 may be provided-in cover 23 in order to observe the spark gap between points-16 and 17.

This particular embodiment of the invention is designed to give high efficiency sparking under extreme operating conditions such as are encountered where a standard motor vehicle is usedfor racing or rallying. It is also particularly suited for use on outboard motors'on boats, hydroplanes and the like.

Referring to F1012, an embodiment of the invention is illustrated wherein the'customary contact breaker set is replaced by a unit type breaker comprising a base 30, having a turned up lip 31 and overhang 32 formed thereon, and a pivot post 33' over as shown at 33a.

Adjustable electrical contact point 38 is carried on member 39 which mates as illustrated with lip and overhang 3] and 32 respectively. Member 39 is further provided with a threaded,

rod 40 which carries knurled wheel 41, the serrations on this wheel 41 being adapted to mate with a leaf spring 42 formed 7 into a hump between retaining wing members 43 and 44. Rod

40 is further supported by bearer member 45 to stabilize the movement of member 39 when wheel 41 is rotated. Flange member 46 on member 39 is adapted for rubbing contact with surface 47 or lip 31 so as to prevent overturn when wheel 41 is rotated so moving member 39 towards or away from contact 35.

Although FIG. 2 illustrates an internally adjusted version of the invention itis to be appreciated that, by extending rod 40; wheel 41, spring 42 and retaining wings 43, and 44may all be placed externally to a standard distributor easing so affording external adjustment while the engine is actually running.

Referring to FIG. 3, an alternative embodiment is illustrated wherein a base 50 is provided with upturned lips 51 and 52 adapted, between them, to carry threaded rod 53 which has a squared end 54 passing through a square hole 55 in'lip 52. Abutting lip 51 is a knurled wheel 56 carried on rod 53, the arrangement being such that wheel 56 can be rotated by the human thumb to press against lip 51 thereby to lock rod 53 against movement. On the side oflip 5 1 opposite to wheel 56 there is an adjustment wheel 57 fast with a threaded tube (FIG. 4) and a tensioning coil spring 58. The tube, which is illustrated in part section in FIG. 4 and identified by numeral 59, is female threaded to accept rod 53 and the arrangement is such that, on rotating wheel 57 rod 53 is drawn into or expelled from tube 59 so moving contact bearing plate 60 (FIG. 3) towards or away from electrical contact 61 on cam follower member 62.

The embodiment illustrated in FIG. 3 is for an internal adjustment contact breaker but, by extending the tube-59 as shown in FIG. 4 external adjustment is achieved. In this illustration numeral 63 denotes the wall of casing 10 of a distributor and 64 denotes a watertight grommet. A cover 65 may overlie spring 58 to assist in the exclusion of dirt or moisture from the interior of the distributor.

Referring to FIGS. 5 and 6 which show single contact point variants for FIG. 3. FIG. 5 shows a variant that is adapted to be adjusted externally to the distributor casing so that the engine may be running during adjustment. FIG. 6 illustrates the same type of contact breaker assembly but restricted to internal adjustmentso that the engine must be stopped while adjustment takes place.

We claim:

1. A contact breaker assembly for use with a distributor of a spark ignited internal combustion engine, comprising a casing located at the exterior of said distributor, a cam follower extending from said casing, a first electrical contact point within said casing associated with said cam follower having a reciprocatory movement in consonance with said cam fol lower, a bearer member within said casing, a second electrical contact point within said casing associated with said bearer member, and hand-operable adjustment means on said casing adapted to open and close the gap between said first and second contact points, said hand-operable adjustment means comprising a knurled wheel associated with resiliently biased restraining means and with a screw threaded rod adapted to selectively progress said second electrical contact point towards and away from said first electrical contact point.

2. A contact breaker assembly as claimed in claim 1 in which said hand-operable adjustment means comprises'a pair of wheels carried on a screw threaded rod, one of said wheels acting as a locking device in association with a threaded bearer member through which said rod passes, the other of said wheels being fast with said screw threaded rod which is adapted to progress said second electrical contact point towards or away from said first electrical contact point. 

1. A contact breaker assembly for use with a distributor of a spark ignited internal combustion engine, comprising a casing located at the exterior of said distributor, a cam follower extending from said casing, a first electrical contact point within said casing associated with said cam follower having a reciprocatory movement in consonance with said cam follower, a bearer member within said casing, a second electrical contact point within said casing associated with said bearer member, and hand-operable adjustment means on said casing adapted to open and close the gap between said first and second contact points, said hand-operable adjustment means comprising a knurled wheel associated with resiliently biased restraining means and with a screw threaded rod adapted to selectively progress said second electrical contact point towards and away from said first electrical contact point.
 2. A contact breaker assembly as claimed in claim 1 in which said hand-operable adjustment means comprises a pair of wheels carried on a screw threaded rod, one of said wheels acting as a locking device in association with a threaded bearer member through which said rod passes, the other of said wheels being fast with said screw threaded rod which is adapted to progress said second electrical contact poiNt towards or away from said first electrical contact point. 